Fabrication of high performance Matrimid/polysulfone dual-layer hollow fiber membranes for O-2/N-2 separation

Matrimid/polysulfone (PSf) dual-layer hollow fiber membranes were fabricated by using co-extrusion and dry-jet wet-spinning phase-inversion techniques. The effects of the spinning dope composition, spinneret dimension, spinneret temperature and the air gap distance on the hollow fiber membranes separation performance were studied. Aging phenomenon was also studied. After coated by 3 wt% silicon solution, the hollow fiber membranes have an O-2/N-2 selectivity of 7.55 at 25 degrees C, 506.625 kPa which exceeds the intrinsic value of Matrimid. The membranes have an O-2 permeance of 9.36 GPU with an apparent dense-layer thickness of 1421 A calculated from the O-2 permeability. SEM images show the high porosity underneath the dense skin. It indicates that non-solvent addition is not necessary in the inner spinning dope to induce the macroviod formation. The binodals of the Matrimid/solvent/H2O and PSf/solvent/H2O indicate that the composition of the spinning dope plays an important role in the structure and the gas separation performance of the dual-layer hollow fiber membranes. The delayed demixing of the inner spinning dope may fabricate low resistance support layers in the dual-layer hollow fiber membranes. (C) 2008 Elsevier B.V. All rights reserved